diff options
Diffstat (limited to 'Documentation/ABI/testing/sysfs-power')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-power | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-power b/Documentation/ABI/testing/sysfs-power new file mode 100644 index 00000000..21777261 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-power @@ -0,0 +1,246 @@ +What: /sys/power/ +Date: August 2006 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power directory will contain files that will + provide a unified interface to the power management + subsystem. + +What: /sys/power/state +Date: August 2006 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/state file controls the system power state. + Reading from this file returns what states are supported, + which is hard-coded to 'standby' (Power-On Suspend), 'mem' + (Suspend-to-RAM), and 'disk' (Suspend-to-Disk). + + Writing to this file one of these strings causes the system to + transition into that state. Please see the file + Documentation/power/states.txt for a description of each of + these states. + +What: /sys/power/disk +Date: September 2006 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/disk file controls the operating mode of the + suspend-to-disk mechanism. Reading from this file returns + the name of the method by which the system will be put to + sleep on the next suspend. There are four methods supported: + 'firmware' - means that the memory image will be saved to disk + by some firmware, in which case we also assume that the + firmware will handle the system suspend. + 'platform' - the memory image will be saved by the kernel and + the system will be put to sleep by the platform driver (e.g. + ACPI or other PM registers). + 'shutdown' - the memory image will be saved by the kernel and + the system will be powered off. + 'reboot' - the memory image will be saved by the kernel and + the system will be rebooted. + + Additionally, /sys/power/disk can be used to turn on one of the + two testing modes of the suspend-to-disk mechanism: 'testproc' + or 'test'. If the suspend-to-disk mechanism is in the + 'testproc' mode, writing 'disk' to /sys/power/state will cause + the kernel to disable nonboot CPUs and freeze tasks, wait for 5 + seconds, unfreeze tasks and enable nonboot CPUs. If it is in + the 'test' mode, writing 'disk' to /sys/power/state will cause + the kernel to disable nonboot CPUs and freeze tasks, shrink + memory, suspend devices, wait for 5 seconds, resume devices, + unfreeze tasks and enable nonboot CPUs. Then, we are able to + look in the log messages and work out, for example, which code + is being slow and which device drivers are misbehaving. + + The suspend-to-disk method may be chosen by writing to this + file one of the accepted strings: + + 'firmware' + 'platform' + 'shutdown' + 'reboot' + 'testproc' + 'test' + + It will only change to 'firmware' or 'platform' if the system + supports that. + +What: /sys/power/image_size +Date: August 2006 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/image_size file controls the size of the image + created by the suspend-to-disk mechanism. It can be written a + string representing a non-negative integer that will be used + as an upper limit of the image size, in bytes. The kernel's + suspend-to-disk code will do its best to ensure the image size + will not exceed this number. However, if it turns out to be + impossible, the kernel will try to suspend anyway using the + smallest image possible. In particular, if "0" is written to + this file, the suspend image will be as small as possible. + + Reading from this file will display the current image size + limit, which is set to 500 MB by default. + +What: /sys/power/pm_trace +Date: August 2006 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/pm_trace file controls the code which saves the + last PM event point in the RTC across reboots, so that you can + debug a machine that just hangs during suspend (or more + commonly, during resume). Namely, the RTC is only used to save + the last PM event point if this file contains '1'. Initially + it contains '0' which may be changed to '1' by writing a + string representing a nonzero integer into it. + + To use this debugging feature you should attempt to suspend + the machine, then reboot it and run + + dmesg -s 1000000 | grep 'hash matches' + + If you do not get any matches (or they appear to be false + positives), it is possible that the last PM event point + referred to a device created by a loadable kernel module. In + this case cat /sys/power/pm_trace_dev_match (see below) after + your system is started up and the kernel modules are loaded. + + CAUTION: Using it will cause your machine's real-time (CMOS) + clock to be set to a random invalid time after a resume. + +What; /sys/power/pm_trace_dev_match +Date: October 2010 +Contact: James Hogan <james@albanarts.com> +Description: + The /sys/power/pm_trace_dev_match file contains the name of the + device associated with the last PM event point saved in the RTC + across reboots when pm_trace has been used. More precisely it + contains the list of current devices (including those + registered by loadable kernel modules since boot) which match + the device hash in the RTC at boot, with a newline after each + one. + + The advantage of this file over the hash matches printed to the + kernel log (see /sys/power/pm_trace), is that it includes + devices created after boot by loadable kernel modules. + + Due to the small hash size necessary to fit in the RTC, it is + possible that more than one device matches the hash, in which + case further investigation is required to determine which + device is causing the problem. Note that genuine RTC clock + values (such as when pm_trace has not been used), can still + match a device and output it's name here. + +What: /sys/power/pm_async +Date: January 2009 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/pm_async file controls the switch allowing the + user space to enable or disable asynchronous suspend and resume + of devices. If enabled, this feature will cause some device + drivers' suspend and resume callbacks to be executed in parallel + with each other and with the main suspend thread. It is enabled + if this file contains "1", which is the default. It may be + disabled by writing "0" to this file, in which case all devices + will be suspended and resumed synchronously. + +What: /sys/power/wakeup_count +Date: July 2010 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/wakeup_count file allows user space to put the + system into a sleep state while taking into account the + concurrent arrival of wakeup events. Reading from it returns + the current number of registered wakeup events and it blocks if + some wakeup events are being processed at the time the file is + read from. Writing to it will only succeed if the current + number of wakeup events is equal to the written value and, if + successful, will make the kernel abort a subsequent transition + to a sleep state if any wakeup events are reported after the + write has returned. + +What: /sys/power/reserved_size +Date: May 2011 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/reserved_size file allows user space to control + the amount of memory reserved for allocations made by device + drivers during the "device freeze" stage of hibernation. It can + be written a string representing a non-negative integer that + will be used as the amount of memory to reserve for allocations + made by device drivers' "freeze" callbacks, in bytes. + + Reading from this file will display the current value, which is + set to 1 MB by default. + +What: /sys/power/autosleep +Date: April 2012 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/autosleep file can be written one of the strings + returned by reads from /sys/power/state. If that happens, a + work item attempting to trigger a transition of the system to + the sleep state represented by that string is queued up. This + attempt will only succeed if there are no active wakeup sources + in the system at that time. After every execution, regardless + of whether or not the attempt to put the system to sleep has + succeeded, the work item requeues itself until user space + writes "off" to /sys/power/autosleep. + + Reading from this file causes the last string successfully + written to it to be returned. + +What: /sys/power/wake_lock +Date: February 2012 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/wake_lock file allows user space to create + wakeup source objects and activate them on demand (if one of + those wakeup sources is active, reads from the + /sys/power/wakeup_count file block or return false). When a + string without white space is written to /sys/power/wake_lock, + it will be assumed to represent a wakeup source name. If there + is a wakeup source object with that name, it will be activated + (unless active already). Otherwise, a new wakeup source object + will be registered, assigned the given name and activated. + If a string written to /sys/power/wake_lock contains white + space, the part of the string preceding the white space will be + regarded as a wakeup source name and handled as descrived above. + The other part of the string will be regarded as a timeout (in + nanoseconds) such that the wakeup source will be automatically + deactivated after it has expired. The timeout, if present, is + set regardless of the current state of the wakeup source object + in question. + + Reads from this file return a string consisting of the names of + wakeup sources created with the help of it that are active at + the moment, separated with spaces. + + +What: /sys/power/wake_unlock +Date: February 2012 +Contact: Rafael J. Wysocki <rjw@sisk.pl> +Description: + The /sys/power/wake_unlock file allows user space to deactivate + wakeup sources created with the help of /sys/power/wake_lock. + When a string is written to /sys/power/wake_unlock, it will be + assumed to represent the name of a wakeup source to deactivate. + If a wakeup source object of that name exists and is active at + the moment, it will be deactivated. + + Reads from this file return a string consisting of the names of + wakeup sources created with the help of /sys/power/wake_lock + that are inactive at the moment, separated with spaces. + +What: /sys/power/pm_print_times +Date: May 2012 +Contact: Sameer Nanda <snanda@chromium.org> +Description: + The /sys/power/pm_print_times file allows user space to + control whether the time taken by devices to suspend and + resume is printed. These prints are useful for hunting down + devices that take too long to suspend or resume. + + Writing a "1" enables this printing while writing a "0" + disables it. The default value is "0". Reading from this file + will display the current value. |